Z Probe Offset calibration

#1

When I installed the v3Dual I neglected to catch my z probe offset… Yea I know always read the manual first… So my question is can one redo the offset that lulzbot ran in the shop ? Ive already asked support a month or two ago for the original numbers but no ones responding; assuming because of the move and change of ownership. I however am tired of waiting so I’d like to figure out the offset on my own in the hopes it will solve my first layer woes.

Does anyone know the procedure? Or does it require lulzbot I.P. that’s not freely available ?

Thanks

Phillip

#2

You can determine the appropriate Z offset experimentally.

Start with a high one (as in, with the nozzle up higher), and see how high off the build plate your initial layer is - at this point, eyeballing it is fine. Adjust the Z offset down to approximately where you think it should be based on that first test print, and do another test print (I’d recommend sticking on the conservative/high side with the offset so you don’t crash/gouge into your PEI sheet).

After your second test print, use the amount of “squish” or “elephant’s foot-ing” you see on the initial layer to decide if you should increase or decrease the Z offset (more squish, move the Z offset up; less squish, move it down). At this point, the recommendation is to only adjust the offset by 0.05 mm at a time.

Repeat this procedure until you get the initial layer printing the way you want (usually people go for just a little bit of “squish” for good bed adhesion).

The “factory” offset is really just a recommendation (good starting point), and the “perfect” offset can change based on the seating of your hot end in the cradle, or your bed geometry after assembly, just to name a couple of variables.

#3

First Off Thank you @cg49me

So I have a good idea where it is now, but i’m still failing prints. Brief description of my observations.

When I kick off a print the first layer doesn’t seem too be level. The right side of the bed printers more or less the proper layer height whereas the left side is extremely thin or non existent. Do these beds warp after time? Also another thing I notice, when I apply like 2 pounds of pressure too the middle of the extruder (pushing it away from me, thus pushing the extruder toward me ), I see filament on the left side extruding properly. It would appear either my bed is warped or the leveling portion isn’t correct. If the leveling portion isn’t correct then wouldn’t that indicate a zprobe offset issue still?

#4

Glass probably won’t warp over time… :slight_smile:

Thin or no filament extruded means the nozzle is too close to the bed… essentially the bed is blocking the nozzle opening and the pressure build-up of filament is pushing the bed enough to allow extrusions.

Check that the metal discs and nozzle aren’t dirty. Any film or residual filament on the disc or nozzle can cause the autolevel (based on electrical continuity) to fail.

#5

Run this test from the console, see how level your bed is in comparison to each washer:
M420 S0 ; shut off auto-leveling
G28 X Y ; home the X & Y axis
G28 Z ; home the Z axis
G29 V4 ; Perform Auto Leveling Test, verbose output

< [19:36:52] Bed X: -3.000 Y: -9.000 Z: 0.665
< [19:37:08] Bed X: 282.000 Y: -9.000 Z: 0.483
< [19:37:26] Bed X: 282.000 Y: 291.000 Z: 0.586
< [19:37:44] Bed X: -3.000 Y: 291.000 Z: 0.410

X: Y: is the position of the washer that the nozzle is at when probing the washer. The Z value is what you’re interested in here. Run this simple test to see how level your bed is.